The invention relates to a portable re-fueling vehicle for providing bulk fuel from a pressurized reservoir. More particularly, this invention relates to a bulk fuel delivery control system in which a fluid driven power source of the system is driven at constant speed by fuel flow.
Major airports are frequently constructed to have large-capacity underground supply reservoirs for providing aircraft fuel. Access to the supply reservoirs is by way of hydrants located below the airport surface but accessible from the surface of the airport. The hydrants are equipped with flow-control valves whose open and closed positions are controlled by pressurized air supplied to the valve by a pneumatic hose under the control of the operator of the re-fueler vehicle.
A re-fueler vehicle of the hydrant type is not equipped with a refueling tank. The essential elements of a hydrant re-fueler vehicle are: a fuel hydrant hose and means for coupling the fuel hydrant hose to the hydrant; a pressurized air hose controllable by the re-fueler operator from a remote position, such as at the fuel intake valve of the aircraft and means for coupling the pressurized-air hose to the hydrant valve; at least one, and preferably two or more, fuel delivery hoses and means for coupling the fuel delivery hoses to the intake valve(s) of the aircraft intake usually located on the undersurface of one of the wings of the aircraft.; and means, usually including filtering means and metering means, inter-connecting the hydrant and delivery fuel hoses on the re-fueler vehicle. No fuel pump is needed on a hydrant re-fueler vehicle. Pressure for causing the fuel to flow from the underground supply reservoirs into the tanks of the aircraft is provided by the underground support facilities at the airport.
Typically, a compressed air source is provided on the re-fueler cart for operating and controlling the hydrant valve and other ancillary components/instrumentation, such as filters, hose reels, etc. For example, it is known to utilize compressed air storage bottles to power such instrumentation. Yet, storage bottles are cumbersome and inconvenient to handle (i.e., re-charge). As such, it is desirable to employ an on-board air compressor on the re-fueler vehicle. Since a combustion engine compressor would pose a significant safety risk when processing bulk fuel, fluid driven air compressors are increasingly employed. The fluid driven air compressor utilizes the pressurized bulk fuel flow as a drive means.
However, present fluid driven air compressors suffer in that the rate of fluid flow varies considerably as the aircraft fuel tank is replenished. As the fuel flow rate diminishes along a main bulk fuel path, a commensurate decrease in fluid flow is provided to the fluid driven air compressor along a motor intake path. It is desirable that a re-fueler vehicle have an on-board air compressor operating at a constant speed.
As such, one known solution has been to provide a specialized mechanical orifice plate along the main fuel path of a re-fueler vehicle for producing a constant back pressure along a fluid motor intake path downstream of the orifice. In operation the orifice is relatively wide for a high flow rate and constricts as the fuel flow rate lessens. As can be appreciated, the orifice plate provides a constant pressure difference thereacross for varying levels of fluid flow provided to the main fuel path. However, the constant pressure difference of the orifice plate does not provide a substantially constant fluid flow along the motor intake path for driving the fluid driven motor at a constant speed. Moreover, the mechanical plate is cost prohibitive and typically requires a fluid motor feedback arrangement for practical use.
Accordingly, there is a need for a simplified and economical bulk fuel delivery system for operating a fluid driven power source at a constant speed.